package com.jwetherell.my.problems.backtracking;

public class KnightTourC {

	int isSafe(int x, int y, int [][] sol)
	{
	    if ( x >= 0 && x < sol. && y >= 0 && y < N && sol[x][y] == -1)
	        return 1;
	    return 0;
	}
	 
	/* A utility function to print solution matrix sol[N][N] */
	void printSolution(int sol[N][N])
	{
	    for (int x = 0; x < N; x++)
	    {
	        for (int y = 0; y < N; y++)
	            printf(" %2d ", sol[x][y]);
	        printf("\n");
	    }
	}
	 
	/* This function solves the Knight Tour problem using Backtracking.  This
	function mainly uses solveKTUtil() to solve the problem. It returns false if
	no complete tour is possible, otherwise return true and prints the tour.
	Please note that there may be more than one solutions, this function
	prints one of the feasible solutions.  */
	bool solveKT()
	{
	    int sol[N][N];
	 
	    /* Initialization of solution matrix */
	    for (int x = 0; x < N; x++)
	        for (int y = 0; y < N; y++)
	            sol[x][y] = -1;
	 
	    /* xMove[] and yMove[] define next move of Knight.
	       xMove[] is for next value of x coordinate
	       yMove[] is for next value of y coordinate */
	    int xMove[8] = {  2, 1, -1, -2, -2, -1,  1,  2 };
	    int yMove[8] = {  1, 2,  2,  1, -1, -2, -2, -1 };
	 
	    // Since the Knight is initially at the first block
	    sol[0][0]  = 0;
	 
	    /* Start from 0,0 and explore all tours using solveKTUtil() */
	    if(solveKTUtil(0, 0, 1, sol, xMove, yMove) == false)
	    {
	        printf("Solution does not exist");
	        return false;
	    }
	    else
	        printSolution(sol);
	 
	    return true;
	}
	 
	/* A recursive utility function to solve Knight Tour problem */
	int solveKTUtil(int x, int y, int movei, int sol[N][N], int xMove[N],
	                int yMove[N])
	{
	   int k, next_x, next_y;
	   if (movei == N*N)
	       return true;
	 
	   /* Try all next moves from the current coordinate x, y */
	   for (k = 0; k < 8; k++)
	   {
	       next_x = x + xMove[k];
	       next_y = y + yMove[k];
	       if (isSafe(next_x, next_y, sol))
	       {
	         sol[next_x][next_y] = movei;
	         if (solveKTUtil(next_x, next_y, movei+1, sol, xMove, yMove) == true)
	             return true;
	         else
	             sol[next_x][next_y] = -1;// backtracking
	       }
	   }
	 
	   return false;
	}
	 
	/* Driver program to test above functions */
	int main()
	{
	    solveKT();
	    getchar();
	    return 0;
	}
	
}
